1. Field of the Invention
This invention pertains to wrapping machines for forming article filled, crimped end style packages formed from a flat web into a tube of wrapping material with the articles spaced therein. The machine simultaneously tucks all four sides of the film inwardly at a single station while evacuating substantially all the air from the packages resulting in a tighter tuck between the end extensions of the packages.
2. Description of the Prior Art
Wrapping machines which form tubes of wrapping material or film around spaced articles are well known in the art. Campbell U.S. Pat. No. 2,546,721 which issued on Mar. 27, 1951 discloses one such machine which forms article filled packages and utilizes pleating rollers on cam operated pivot arms to tuck in the package sides at a station upstream of the transverse crimping and cutoff station. Cam operated tuckers are now common in the art, however the method does not permit minimization of package length because the tuckers do not travel with the web while tucking and also cam pressure angles become excessive. The tucking operation reliability suffers when attempts are made to minimize package length.
The United States Patents to Kraft U.S. Pat. Nos. 3,090,174 which issued on May 21, 1973 and 3,439,174 which issued on Apr. 22, 1969 disclose the combination of a sealer and a tucker which provides tight tucks between spaced articles in a tube of wrapping material by tucking the material inwardly from all four sides. However, the Kraft patents utilize a series of equally spaced flexible tucking lugs attached to upper and lower flexible belts for tucking the upper and lower walls of a tube of wrapping material inwardly. Thus, Kraft's upper and lower tucker lugs are limited to a specific package size and cannot be adjusted to accommodate packages of different sizes. Kraft's unheated tucking lugs do not tack the flap material together at the tuck, and accordingly must remain in contact with the packaging material for a substantial linear distance and up to a point immediately adjacent the sealer.